This invention relates to escalators and more particularly to curved escalators which have a stairway path that is curved in plan.
Typical circular or curved escalators have a stairway path along which a series of steps travel, the path having a constant radius of curvature in plan throughout its entire length including the horizontally-moving landing sections at the upper and lower ends of the escalator. The stairway path is defined by guide rails that support and guide various rollers mounted on the steps. The guide rail on the outer side of the circular stairway path and the guide rail on the inner side of the circular stairway path are different in gradient. Therefore, with guide rail of a constant radius of curvature as in the escalator described above, the distance between the axes of step axles that connect the step to the driving chain must be variable in order that the angular velocities of the step at the outer and inner side of the step be equal even in locations where the angle of slope changes, and as in the transition portions between the load-bearing inclined portion and the upper or lower horizontal landing portion. This requires a complex and expensive driving and guiding arrangement in the escalator.
In order to solve the above problems in curved escalators, U.S. patent application Ser. No. 526,132 proposes a curved escalator in which the radius of curvature of the guide tracks defining a stairway path when viewed in plan is inversely proportional to the slope of the various sections of the stairway path.
This application, however, is silent about the detailed arrangement for maintaining clearance between outer and inner skirt guards and side faces of the steps so as to be always constant. Therefore the clearances between the skirt guards and the steps vary according to the position of the steps along the stairway path, posing the danger of foreign matter such as a passenger's foot being caught in the clearance. Also, the distance between the step and a moving hand rail on the balustrade varies along the stairway path of the escalator, again posing a similar danger for the passenger.
Furthermore, inner panels on the balustrade for a curved escalator is disclosed in the above-mentioned U.S. patent application are formed in a three dimensional shape. The three-dimensionally curved panel is much more expensive than other two-dimensional panels.